Lever actuated machine-tool chuck



March 31, 1959 J-M GAMET 9 LEVER ACTUATED MACHINE-TOOL CHUCK Filed June 4, 1956 2 Sheets-Sheet 1 March 31, 1959 J-M GAMET LEVER ACTUATED MACHINE-TOOL CHUCK 2 Sheets-Sheet 2 Filed June 4, 1956 g Q i K N w United States Patent Chucks for machine-tools are already known which can be operated while running by means of jacks; these chucks have generally three jaws. "Thus, a singl e operating member actuated by the jack'and acting on these three jaws simultaneously'can provide a balanced grip on a work-piece to be machined inthe chuck.

In certain cases however, the form of the work-pieces to be machined is such that it is necessary to grip them with four jaws arranged in oppositepairs (in the case of four-sided work-pieces or members with opposite flats).

If the four jaws are actuated by the same operating member, a balanced grip of the work-piece cannotbe obtained, since a clamping system of this kind is hyperstatic.

The present invention has for its object a chuck with four jaws and its operating mechanism, which enables a practically-balanced clamping action to be obtained by the four jaws on the work-piece to be held.

In accordance with the invention, the'four jaws arranged in opposite pairs are displaced radially in the chuck by'four equal levers twoby two, the levers cor responding to one pair of opposite jaws being directed in the opposite sense to the levers corresponding to the other pair, and two members coaxial to the chuck act on the two pairs of levers, the said members being connected, one to the cylinder and the other to the piston of a" fluid jack which is free to move along the axis of the said chuck.

Thus when the jack is put under pressure, the piston and the cylinder of the jack move in opposite'direction which gives rise to radial displacements of the four jaws in the same direction, by reason of the reverse arrangement of the two pairs of levers. In addition, as soon as one of the pair of jaws has made contact with the work-piece to be held, the other continues to move radiallyuntil the four jaws have all made contact with the work-piece and clamp this latter.

The four jaws' are preferably arranged at the same radial distance from the axis of the-work-piece to be clamped, and the four levers are equal; In this case, by reason of the equality of the oppositely-directedforces which are produced in the jack, and the equality of the levers, the four jaws are finally equally tightened. In fact, for each pair of jaws, the forces on each of them are equal and directly opposed, whilst the forces are balanced on the two pairs of jaws by virtue of the equality of action and reaction inthe forces developed into the jack.

In a construction of this kind, the two opposite pairs of jaws may be arranged at right angles in the jack; they may also be arranged at any other desired angle. The operating jack is preferably of the rotary type supplied by a rotating distributor which accompanies the axial movement of translation of the jack.

The description which follows below with reference to the attached drawings (which are given by way of example only and not in any sense byway of limitation) ice 2 will make it quite clear how the invention may be carried into efiect. i

'Fig. 1 shows a front view of a chuck with four jaws. Fig. 2 is a developed cross-section along the line II-''II of Fig. l of the chuck and its operatingmechanism.

' Fig. 3 is a detail view in perspective of the actuating member of the levers of the chuck. The chuck shown in Figs. 1 and 2 is carried on the nose of a spindle 1 which rotates in a head-stock 2 of a machine-tool driven by means of a pulley 3 and a trapezoidal belt 4. The chuck is centered on this spindle by a conical'mounting to which it is fixed in the usual manner, for example by means of screws. The chuck is constituted by'two parts 6 and 1 assembled together, in which hollowed-out portions facing each other form the emplacement of the levers 8a and 9a.

' The lever 82: corresponds to a jaw-carrier 10a which slides radially in the chuck and which carries a jaw 11a in known manner, fixed by means of blocks and screws 12. At a position diametrically opposite to the jaw-carrier 10a and to the jaw 11a, is arranged a further jaw carrier 10b carrying a jaw 11b. The jaw-carrier 10b is operated by a lever 8b (not shown) which is identical with the lever 8a but diametrically opposite thereto.

The lever 9a corresponds to a jaw-carrier 1311 which carries a jaw 14a; Opposite to the jaw-carrier 13a and the'jaw 14a is arranged the jaw-carrier 13b and the jaw 14b which are operated by the lever 9b (not shown) diametrically opposite to the lever 9a and which is arranged in the same way as this latter lever.

The levers 8a; 8b, 921, 9b areadapted to pivot about pins 15 located in thesarne plane perpendicular to the axis of the chuck and at the same distance from said axis. 'In' addition, these levers are each constituted by an eccentric portion 16a, 17a (and 16b, 17b, not shown) which is in contact with the opposite faces 18a, 19a, 20a, 21a ofcavities formed in the'present casein the jawcarriers 10a and 13. Each of these eccentrics is rigidly secured with an arm 22a, 23a for the levers 8a and 9a.

As canbe seen from Fig. 2, the two levers 8a and 9a and in consequence the two levers 8b and 9b (notshown) are oppositely directed, that is to say, in order to obtain for example 'a movement of the jaw-carrier 10a towards the axis, it is necessary 'to act on the arm'22a in thedirection of the arrow F, whilst in order to obtain a movement towards the axis of the jaw-carrier 13a, action must be taken in the opposite direction (arrow G) on the arm 23aof the lever 9a.

The two extremities of the arms 22a and 22b (the latter not being shown) of the levers 8a and 8b are re spectively engaged in the grooved portions 24a and 24b of amernber 25 which is movable in an axial direction. This member 25 is constituted, as shown in Fig. 3, by two diametrically-opposite segments of a cylinder coupled together by a circular central portion. Ina similar man net, the extremities of the two arms 23a and 235 are respectively engaged in thegrooved portions 28a and 28b of a second member 29 similar in shape to the member 25, that is to say comprising two diametrically-opposite cylindrical segments which engage with the corresponding portionsof the member 25, in such manner thatthe periphery of the two engaged-members forms practically a complete cylinder.- 1 I The two members 25 and 29 can slide in the central portion of thechuck, but they are prevented from rotating with respect to the chuck by means of a finger 26 fixed in the plate 27 (provided with openings for the passage of the jaws) which form the frontface'of the chuck, the said finger passing into a hole drilled in the membcr 25.

In the member 29, a tube 30 is fixed, for example by screwing, and a concentric tube 31 is also fixed in the member 25. It will be noted that the tube 31 forms, over the whole length of the device, a longitudinal channel which enables the machining in the chuck of bars of indefinite length and also permits of the introduction of cooling fluid into the centre or again an exploratory control ensuring the automatic closure of the chuck 'when the. work-piece to be machined is introduced into the aws.

On the opposite side of the chuck with respect to the head-stock 2, the actuating jack of the said chuck is able to slide on the extremity of the spindle 1. This jack comprises an annular piston 32 which is rigidly fixed to the tube 30 by means of a nut 33 and a lock-nut 34. This piston is contained in the cylinder 35 which is in two parts assembled together by means of screws 36, which cylinder can slide longitudinally with respect to the piston and which is fixed to the tube 31 through the intermediary of the cup-shaped member 37. This cup is fixed to the cylinder 35 by the screws 38 and to the tube 31 by the nut and the lock-nut 39 and 40 respectively.

The cylinder and the piston are secured for rotation by a finger 41 which, during the movement of the piston with respect to the cylinder,-engages in the hole 42 drilled in the body of the cylinder. The piston and the cylinder are rotatably driven together at the same speed as the spindle, for example by means of a finger 43 which, in the. example shown, is fixed on the pulley 3 and engages in a hole 44 bored in the body of the cylinder 35. The whole assembly is enclosed in a casing 45 which forms a collector of leakage from the distributor of the jack, as will be described later. Frictionless fluid-tight grooves 46 and 47, provided with oil return slots 46a and 47a prevent all leakage of oil to the exterior. Inside the casing 45 is fixed the distributor 48 which provides for the alternate supply of fluid to the two compartments of the jack. This distributor comprises the couplings 49 and 50 to flexible conduits for the supply of oil under pressure and the return circuit of the oil.

The rotating extension 35a of the cylinder 35 carries a ring 51 which is centered in the fixed distributor 48 without making contact therewith. This centering without contact is obtained by means of roller bearings 52. The conduits 49 and 50 deliver into peripheral grooves 53 and 54 respectively of the distributor 48, and the ring 51 together with the body of the cylinder 35 are provided with channels 55 and 56 respectively which provide a communication between the conduits 49 and 50 and the compartments of the jack.

When oil under pressure is applied to one of the conduits 49 or 50, this oil is directed through the groove and the channel corresponding into one of the compartments of the jack and there is produced a slight leakage of oil at a limited and controlled rate, between the distributor 48 and the ring 51, this leakage being provided to lubricate the bearings 52 which are thereby cooled at the same time. The oil which has thus escaped is collected in the bottom of the casing 45 and is evacuated through the collector nozzle 57 which returns this oil to the supply tank. This nozzle 57 is also coupled to the said tank by a flexible conduit and, in the present case, this nozzle is employed in conjunction with a lug 58 fixed to the general framework 59 of the machine in order to prevent rotation of the casing 45 of the jack whilst at the same time permitting a free sliding longitudinal movement of the assembly of the jack and its casing.

It will be assumed that with the device shown in Fig. 2 it is desired to ensure the clamping of the exterior of a work-piece located between the jaws 11a, 11b, 14a, 14b. In the position shown in Fig. 2, oil under pressure is sent into the conduit 49 and is delivered into the'lefthand compartment of the jack. This oil under pressure applies a thrust towards the right on thepiston 32 and, at the same time, the same thrust towards the left is applied to the cylinder 35a. By virtue of the coupling of these two members respectively by the tubes 30 and 31 with the members 29 and 25, the two levers 9a and 9b are pushed in the direction G and the two levers 8a and 8b are pulled in the direction F. One of the opposite pairs of jaws then comes into contact with the member to be gripped and, as the jack continues to extend, the other pair of jaws comes in its turn into contact with the said member. As the surfaces on which the oil under pressure acts are the same for the piston and for the jack, the tractive force in the direction F is the same as the thrust force in the direction G and, since the levers 8 are equal to the levers 9, the gripping force is equally divided between the four jaws.

If the gripping diameters of the opposite pairs of jaws are different, the lengths of the levers 8 and 9 may be adapted in this case to these differences in gripping diameters and in order to obtain a balanced clamping action, it is necessary that the pair of jaws which acts on the greater of the two clamping diameters should be actuated by a pair of levers which are shorter than those which act on the smaller clamping diameter.

The release of the chuck and also the clamping action on the exterior, as the case may be, are obtained by changing over the intake and return oil circuits, that is to say by sending the oil under pressure through the nozzle 50, the oil return being elfected through the nozzle 49 (arrows in dotted lines).

As is well known, the diameter of the eccentrics and their degree of eccentricity may be such that once the gripping action has been applied, this grip is retained without it being necessary to apply the oil pressure continuously in the jack. Premature releases of the workpieces are thus avoided in the event of leakages in the conduit system or of breakages of these latter.

It will of course be understood that modifications may be made to the forms of embodiment which have just been described above in particular by the substitution of equivalent technical means, without thereby departing from the spirit or from the scope of the present invention.

What I claim is:

1. A clamping device for work-pieces on a machinetool spindle comprising a chuck secured to said spindle and having two pairs of radially displaceable opposite jaws; a first pair of equal leverage means for radially reciprocating one pair of jaws; a second pair of equal leverage means oppositely directed with respect to the said first pair for radially reciprocating the other pair of jaws; two elongated, coaxially arranged members concentric with said chuck and spindle and respectively connected with each pair of said leverage means, and a fluid operated jack comprising a piston reciprocating in a cylinder coaxial with said spindle and adapted to move freely with respect thereto, said piston being connected to one of said elongated members and said cylinder to the other and means for introducing an actuating fluid into said jack to operate the latter.

A clamping device for work-pieces on a machinetool spindle comprising a chuck secured to said spindle and having two pairs of radially displaceable opposite jaws; a first pair of levers having equal radial arms directed with respect to said chuck for radially reciprocating one pair of jaws; a second pair of levers oppositely directed with respect to said first pair of levers and having equal radial arms internally directed with respect to said chuck for radially reciprocating the second pair of jaws; a first member formed by two diametrically-opposite segmental portions of a cylinder coaxial to said chuck and having a peripheral groove engaging the internal ends of said first arms; a second member formed by two diametrically-opposite segmental portions of a cylinder coaxial to said chuck and having a peripheral groove engaging the internal ends of said second arms,

said second member being fitted into the first one; two

coaxial tubular members concentric with said spindle,

and respectively connected with each of said members; an annular jack piston sliding on said spindle and connected to the end of the outer of said tubular members; and a jack cylinder enclosing said piston and longitudinally movable with respect to said spindle and connected to the end of the inner of said tubular members and means for introducing an actuating fluid into said cylinder.

3. A device according to claim 2 further comprising a casing enclosing said piston and cylinder and stationary slide means for preventing rotation of said casing and permitting displacement of said casing in the longitudinal direction of said spindle.

4. A clamping device for work-pieces according to claim 2 wherein said piston and said cylinder are fast with said tubular members and further comprising axially directed finger means fast with said spindle and slidingly engaged into said cylinder and further axially directed finger means fast with said piston and slidingly engaged into said cylinder, whereby said cylinder and piston are driven by said spindle.

5. A machine-tool chuck comprising a cylindrical, axially apertured body, having a front part formed with four rectangular slide channels and four bores, in the same cross-section of said body and at the same distance of the axis thereof, each bore crossing perpendicularly one of the said channels; two pairs of opposite jaws, each jaw sliding in one channel and having towards the rear part of said body, a first transverse recess with two faces in parallel relationship with the corresponding bore and with the axis of said body, and a second radial recess extending from said first recess to the inner end of said jaw; an axle disposed in each of said bores; a lever pivoted about each of said axles and comprising a cylindrical portion tangentially contacting said both faces of said first recess and eccentrically carried with respect to the said axles, and a radial arm extending in said second recess, the pair of levers corresponding to one pair of jaws being oppositely directed with respect to the other pair of levers; a first member formed by two diametrically-opposite segmental portions of a cylinder, coaxially housed in the axial aperture of said body and have a peripheral groove engaging the internal ends of one pair of said lever arms; and a second member formed by two diametrically opposite segmental portions of a cylinder, fitted into said first member and having a pcripheral groove engaging the internal ends of the other pair of lever arms.

References Cited in the file of this patent UNITED STATES PATENTS 534,812 Carlinet Feb. 26, 1895 1,968,700 Milotta July 31, 1934 1,999,031 Burger Apr. 23, 1935 2,568,092 Sloan et a1. Sept. 18, 1951 FOREIGN PATENTS 761,157 Great Britain Nov. 14, 1956 

